1. Field of the Invention
This invention relates to punch-type of tooling for use in punching devices such as turret presses.
2. Prior Art
It is known to provide a punch and stripping guide assembly which includes a stripper sleeve guiding a punch having a threaded upper end encircled by a stripping spring that is preloaded by means of a threaded punch head received on such punch. Such threaded punch head is susceptible to rotation as a consequence of the vibrations and shocks that are incident to usage, and therefore set screws have been used to hold such punch heads in "locked" position at a selected amount of spring compression or length. However, the threaded set screws are just as susceptible to loosening, thus leaving the punch head free to turn and to change its adjustment.
In a press of the turret type, there is a certain amount of clearance between the top of a turret on which tooling is supported and the lower surface of the ram or ram plate with which a selected tool assembly registers. Further, it is not always possible to know exactly what that clearance will be because the retracted position of the ram in a high-speed press may vary because a clutch or brake on a drive shaft which provides one complete punching stroke per revolution is not always stopped with the ram at its most retracted point. For example, a design clearance between the ram and the tooling of one-sixteenth inch in practice typically becomes one thirty-second inch, plus or minus one thirty-second inch. Thus with approximately zero clearance any loosening of such punch head as a consequence of shock and vibration not only has altered the length of die penetration in the workpiece but has provided an overall length of tooling which the turret press could not cope with.